The invention relates to an adjustment device for adjusting the relative rotational angle position of a camshaft in relation to a crankshaft of an internal combustion engine, with the device comprising an adjustment mechanism, which is embodied as a triple-shaft transmission and provided with an input part fixed to the crankshaft, an output part fixed to the camshaft, and an adjusting shaft connected to an adjusting motor shaft of an adjusting motor.
In modern internal combustion engines, a camshaft adjuster is used for varying the timing of gas-exchange valves, whereby an improvement in consumption and output is achieved over the entire load and rpm range. It is known that camshaft adjusters can be actuated hydraulically. Conventional, hydraulically actuated camshaft adjusters (axial piston adjusters, vane cells, pivoting vanes and segmented vanes) have the advantage that the hydraulic valve required for control does not have to be arranged directly axially in front of the adjuster, but instead can be mounted off-center at a position, where sufficient installation space is available for the valve. The oil is led via bore holes in the cylinder head to the adjuster. Therefore, hydraulic camshaft adjusters are built very short and can also be installed under tight installation conditions. Because the adjustment is realized by the pressure of motor oil in conventional, hydraulic camshaft adjusters, the function of the camshaft adjuster is very dependent on the temperature of the motor oil. At low temperatures and thus thick oil, the camshaft adjuster responds not at all or only sluggishly due to the low volume flow. At high temperatures and thus very thin oil, a high pressure is not established, which is why a slow adjustment is also realized under this condition. In addition, the oil pressure and thus the function of the camshaft adjuster depends on the rpm of the internal combustion engine.
These disadvantages do not appear in an electric camshaft adjuster built from an electric motor and adjustment mechanism. However, as provided, for example, from the publication DE 4110195 A1, conventionally this adjuster is embodied such that the electric motor is arranged axially in front of the adjustment mechanism and thus requires a large amount of axial installation space.